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Bituminous waterproofing systems are designed to protect residential and commercial buildings. Bitumen is a mixed substance made up of organic liquids that are highly sticky and viscous, and are waterproof.
Roofing felt components
Bituminous membranes are made up of more than one product:
- Bitumen - Mixed with a filler component such as limestone or sand. Polymers are added to the bitumen such as APP (atactic polypropylene) a plastic additive that gives rigidity and tear resistance, or SBS (styrene butadiene styrene) a rubber additive that gives more elastic benefits.
- Base Products - Polyester, fibre glass, rag fibre (hessian), and paper. These products are bought in roll format and are pulled through the bitumen mixes on huge rollers. The base product becomes saturated in huge tanks by the tar like bitumen substance, creating rolls of waterproof material.
- Mineral - (Optional) Small granules are added to the top of the felt, decreasing the products fire vulnerability.
- Thin, transparent film - This product is added to the base of the felt during manufacturing on all torch-on products. This stops the felt from sticking to itself when rolled up during the packaging process.
The complex chemical composition of bitumen makes it difficult to identify the specific component(s) responsible for adverse health effects observed in exposed workers. Known carcinogens have been found in bitumen fumes generated at work sites. Observations of acute irritation in workers from airborne and dermal exposures to fumes and aerosols and the potential for chronic health effects, including cancer, warrant continued diligence in the control of exposures.
Bituminous roofing products are used for waterproofing roofs on buildings.
- Benefits include that they move with the structure and do not absorb water. Bitumen is a hydrocarbon and is created from crude oil.
- The products have an extremely long life span, with most membranes having BS (British Standards) marks against each product name.
- There is low noise pollution during application.
- Bituminous membranes protect insulation and can reflect harmful sun rays. New products also contain photovoltaic cells that can produce solar energy.
- Bitumen is not water soluble, non-biodegradable
- Bitumen is produced from crude oil and is not regarded as a sustainable building product
- Bitumen is highly flammable
- The bituminous roofing is exposed to extreme heat and UV radiation which decreases the lifespan drastically, protecting the roofing from direct UV radiation is important
- The fumes that are produced during application can cause dermal and respiratory problems
From 1905 to 1988 The Paraffine Paint Co. of San Francisco had Malthoid as a trademark for waterproof and weatherproof building and roofing materials made of paper and felt in whole or in part. However, it had become well known before that. About 1913 Paraffine promoted its Malthoid roofing materials with a 16 page booklet. In 1941 the Duroid Company began making Malthoid in Onehunga, New Zealand.
Malthoid was once common enough to be used as a generic description of flat roofing material in New Zealand and South Africa (item 26). A description of a New Zealand house built about 1914 says it was, "built of timber framework. covered by sheets of asbestos. The roof was closely timbered, then covered by strips of Malthoid paper. This was then painted with tar and topped off with a sprinkling of sand." Railway vehicles in Australia were roofed with Malthoid. Malthoid is still available for flat roofs and damp courses.
- LegalForce information on trademark
- Manawatu Times, Volume XXVII, Issue 7998, 21 June 1904
- Powerhouse Museum. "93/281/1 Brochure, 'Malthoid Bungalows', paper, The Paraffine Paint Company, USA, c. 1913". Powerhouse Museum, Australia. Retrieved 21 September 2013. Read more: http://www.powerhousemuseum.com/collection/database/?irn=132940#ixzz2fVrDXkhm Under Creative Commons License: Attribution Non-Commercial
- Scie Construction Ltd history of flat roofing materials.
- Off the Sheep's Back: Bill Richards Lindon Pub., 1986 ISBN 0864700148, 9780864700148
- photo and some history of Malthoid on Australian heritage railways.
- Tremco technical specs